Measurement of low-frequency respiratory impedance in infants

Sly, P.D., Hayden, M.J., Petak, F. and Hantos, Z. (1996) Measurement of low-frequency respiratory impedance in infants. American Journal of Respiratory and Critical Care Medicine, 154 1: 161-166.

Author Sly, P.D.
Hayden, M.J.
Petak, F.
Hantos, Z.
Title Measurement of low-frequency respiratory impedance in infants
Journal name American Journal of Respiratory and Critical Care Medicine   Check publisher's open access policy
ISSN 1073-449X
Publication date 1996-07
Sub-type Article (original research)
Volume 154
Issue 1
Start page 161
End page 166
Total pages 6
Place of publication New York, NY, United States
Publisher American Thoracic Society
Language eng
Formatted abstract
Low-frequency respiratory impedance (Zrs) data permit the separate estimation of the mechanical properties of the airways and the tissues, but they are difficult to collect in humans because of the need for apneic conditions. We exploited the apneic phase produced by invoking the Hering- Breuer reflex with end-inspiratory airway occlusion in five sedated infants aged 9 to 16 mo. A computer-controlled pump and solenoid valves were used to inflate the supine infants through a face mask to a transrespiratory pressure of 20 cm H2O and to affect the airway occlusion. A loudspeaker-in-box system was connected to the mask through a side-arm, and small-amplitude pseudorandom oscillations containing 23 frequency components between 0.5 and 20.75 Hz were applied for 6 s. Four consecutive measurements were made in each infant, and the averaged Zrs spectra were evaluated on the basis of a model containing the frequency-independent resistance (Raw) and inertance (law) of the airways, and the viscous damping (G) and elastance (H) parameters of the constant-phase compartment of the chest wall and parenchymal tissues. The measured Zrs values were consistent with the model up to 15 Hz, and the average fitting error was 0.89 ± 0.11 (SD) cm H2O.s/L. The following parameter values were obtained: Raw = 10.0 ± 2.1 cm H2O.s/L, law = 0.061 ± 0.014 cm H2O.s2/L, G = 28.6 ± 4.9 cm H2O/L, H = 141 ± 55 cm H2O/L. The tissue hysteresivity (G/H) values were 0.218 ± 0.061. Our results indicate that, in short apneic periods evoked by the Hering-Breuer reflex, reliable low-frequency Zrs data can be collected to partition the tissue and airway impedances in sedated infants.
Keyword Forced oscillations
Pulmonary impedance
Ventilatory system
Input impedance
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Medicine Publications
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Created: Wed, 17 Nov 2010, 11:50:06 EST